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ABSTRACT: We developed a novel fabrication process for the stacked dense integration of a microring resonator (MRR) buried in a SiO<sub>2</sub> cladding with vacuum cladding in the lateral direction. Owing to the vertical coupling and the lateral vacuum cladding, the radiation loss can be greatly reduced without affecting the coupling strength between the busline waveguide and the MRR. The reduction of radiation loss by ten orders of magnitude compared with the SiO<sub>2</sub> buried cladding was theoretically and experimentally demonstrated. Using this technique, an ultracompact vertically coupled MRR with the ring radius of 5 μm was realized, and the free spectral range of 29 nm was successfully obtained.
IEEE Photonics Technology Letters 02/2005; · 2.19 Impact Factor
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ABSTRACT: To eliminate the scattering loss at the crossing points of cross-grid busline waveguides, the multilevel crossing structure of the busline waveguides was introduced into a vertically coupled microring resonator (VCMRR) filter. To achieve this structure, two fabrication technologies were newly developed; one is a method to planarize perfectly the top surface of each buried waveguide, and the other is a method to fabricate microring waveguides with very smooth sidewalls. Using the latter method, an ultracompact VCMRR with a ring radius of 5 μm was realized and a free spectral range of 37 nm was successfully demonstrated. Next, using the former method, single-ring and quadruple series-coupled ring resonators with multilevel crossing busline waveguides were fabricated. A clear filter response was obtained for the single-microring resonator, and a boxlike filter response was obtained for the quadruple series-coupled microring resonator with multilevel crossing busline waveguides.
IEEE Journal of Selected Topics in Quantum Electronics 02/2005; · 3.78 Impact Factor
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ABSTRACT: To eliminate the scattering loss at the crossing points of cross grid busline waveguides, a multilevel crossing structure of busline waveguide was introduced into the vertically coupled microring resonator filter. The top surface of each buried waveguide was perfectly planarized by a new fabrication process and clear filter responses were observed for a single ring and a series coupled double ring resonator with multilevel crossing busline waveguides.
IEEE Photonics Technology Letters 03/2004; · 2.19 Impact Factor
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ABSTRACT: To eliminate the scattering loss at the crossing points of busline waveguides, a multilevel crossing structure of busline waveguide was introduced into the vertically coupled microring resonator filter. The top surface of each buried waveguide was perfectly planarized by a new fabrication process and clear filter responses were observed for a single ring and a double series coupled ring resonator with multilevel crossing busline waveguides.
Lasers and Electro-Optics, 2003. CLEO/Pacific Rim 2003. The 5th Pacific Rim Conference on; 01/2004
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ABSTRACT: The relationship between the spectral efficiency and the crosstalk caused by the wavelength filter in DWDM systems was investigated. The bit rate and the wavelength channel spacing were optimally designed to minimize both the interchannel crosstalk and the intersymbol interference. We showed that the coherent crosstalk occurs at the frequency of about half of the channel spacing and it strongly deteriorates the total crosstalk.
IEEE Photonics Technology Letters 12/2003; · 2.19 Impact Factor
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ABSTRACT: The Lorentzian-shape filter response of a microring resonator filter is not suitable for practical use in wavelength division multiplexing (WDM) systems because of the lack of passband flatness, high crosstalk, and the large wing in the rejection band. Therefore, the tailoring of filter response shape is required to improve the performance. The series coupled microring resonator is one of the solutions. We designed and fabricated vertically triple coupled microring resonator add/drop filters with a stacked configuration. A box-like filter response with a flat passband was successfully obtained, and the free spectral range (FSR) was expanded to 25.8 nm owing to the Vernier effect.
Journal of Lightwave Technology 09/2002; · 2.78 Impact Factor
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ABSTRACT: The vertically coupled microring resonator filter is an attractive add-drop wavelength filter due to its functionality and compactness and the possibility of dense integration resulting from the cross-grid configuration. However, in the concatenated 1 × 8 filter array in which the ring radii are changed with the increments of 50 nm, the wavelength channel spacing was limited to 5.7 nm due to the resolution limit of photomask (50 nm). Therefore, we developed a new technique to control precisely the channel spacing by an ultraviolet (UV)-trimming technique using polysilane as the over-cladding layer. As a result, we successfully decreased the channel spacing to 0.5 nm, and also controlled the channel spacing precisely to 1.0 nm using the same trimming technique
Journal of Lightwave Technology 05/2002; 20(4):745-750. · 2.78 Impact Factor
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ABSTRACT: In the multi-channel microring resonator filter, the wavelength channel spacing was limited to 5.7 nm due to the resolution limit of the photomask (50 nm). Therefore, we developed a new technique to control precisely the channel spacing by a UV-trimming technique using polysilane as the over-cladding layer. As a result, we successfully decreased the channel spacing to 0.5 nm, and also controlled the channel spacing precisely to 1.0 nm using the same trimming technique.
Fibre and Optical Passive Components, 2002. Proceedings of 2002 IEEE/LEOS Workshop on; 02/2002
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ABSTRACT: The input/output coupling loss of vertically coupled microring resonator filters was improved by introducing busline waveguides with large spot size, i.e. the ARROW-type waveguide and the rectangular busline waveguide with a spot size transformer. Clear dropping responses were demonstrated for the ARROW based microring resonator filters and the coupling loss was successfully reduced by 22 dB.
Fibre and Optical Passive Components, 2002. Proceedings of 2002 IEEE/LEOS Workshop on; 02/2002
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ABSTRACT: The ultrashort optical pulse transmission characteristics of a vertically coupled microring resonator (VCMRR) filter were measured at 1.55 μm wavelength, and the transmission capacity per channel was evaluated. The pulsewidth at the output was measured to be 3.4 ps, when 1.2 ps input pulse with a sech pulse shape from a fiber laser was incident on the microring resonator filter with a fullwidth at half-maximum (FWHM) of 0.75 nm (94 GHz). From this result, the maximum transmission capacity of the filter was estimated to be approximately 50 Gb/s. The pulse broadening through the filter was theoretically analyzed, and it was confirmed that the pulse broadening evaluated from the bandwidth of the filter spectrum response were in good agreement with the measured results
Journal of Lightwave Technology 03/2001; 19(2):266-271. · 2.78 Impact Factor
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ABSTRACT: Triple coupled microring resonator add/drop filters with stacked configuration were designed and fabricated. The box-like filter response with a flat pass band was successfully obtained and the FSR was extended to 25.8 nm owing to the Vernier effect.
Optical Communication, 2001. ECOC '01. 27th European Conference on; 02/2001
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ABSTRACT: The temperature dependence of vertically coupled glass microring resonator add/drop filters is investigated. Measurements show that the passband of the air-clad microring resonator filter increases with temperature at a rate of 0.0137 mm//spl deg/C. Using a PMMA-TFMA polymer that has an opposite refractive index temperature gradient than glass as the overlay of the microring resonator, the temperature dependence of the filter is compensated to -0.0025 nm//spl deg/C in the operation range of 25/spl deg/C to 55/spl deg/C.
IEEE Photonics Technology Letters 10/1999; · 2.19 Impact Factor
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ABSTRACT: An antiresonant reflecting optical waveguide (ARROW)-type vertical coupler filter (VCF) with a polysilane cover layer is designed and fabricated to demonstrate the trimming of the center wavelength of the filter by ultraviolet (UV) irradiation. The propagation constant of the upper waveguide of the VCF was modified by UV irradiation on the polysilane cover in the presence of oxygen. The refractive index of polysilane can be adjusted from 1.448 to 1.427 by the exposure time of the UV irradiation. A wide trimming range of 59 nm (1567.5 nm to 1508.8 nm) of center wavelength is demonstrated.
IEEE Photonics Technology Letters 04/1999; · 2.19 Impact Factor
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ABSTRACT: A vertical coupler filter with a polysilane cover layer is fabricated for the trimming of the center wavelength of the filter by UV irradiation. A wide trimming range of 59 nm is demonstrated
Optical Fiber Communication Conference, 1999, and the International Conference on Integrated Optics and Optical Fiber Communication. OFC/IOOC '99. Technical Digest; 02/1999
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ABSTRACT: In this paper, we propose a new evaluation concept for characterizing multimode optical branching waveguides. In a ray tracing to simulate multimode branching waveguides, we introduce a phase space expression with the ray position and slope in order to describe the modal distribution of guided light. We have applied this technique for branching waveguides, which have a parabolic distributed-index, and clarified branching characteristics. Experimental results obtained for diffused branching waveguides are compared with theory.
Journal of Lightwave Technology 11/1986; · 2.78 Impact Factor
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ABSTRACT: A new multimode optical star coupler with a mesh waveguide configuration is proposed to reduce the device length by stimulating light mixing in a short waveguide. A 4Ã4 optical star coupler has been fabricated and its branching variation of 2.8 dB is realised with the device length as short as 14.5 mm.
Electronics Letters 02/1985; · 0.96 Impact Factor
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ABSTRACT: A novel mode scrambler for multimode optical waveguides is proposed to stabilise branching characteristics against the mode excitation conditio. A 2 Ã 2 optical star coupler is fabricated using this mode scrambler, and a stable branching ratio is realised with an excess insertion loss of 2.7 dB.
Electronics Letters 02/1983; · 0.96 Impact Factor
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[show abstract]
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ABSTRACT: To eliminate the sattering loss at the crossing points of cross grid busline waveguides, a multilevel crossing structure of busline waveguide was introduced into the vertically coupled microring resonator filter. The top surface of each buried waveguide was perfectly planarized by a new fabrication process and clear filter responses were observed for a single ring and a series coupled double ring resonator with multilevel crossing busline waveguides.
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[show abstract]
[hide abstract]
ABSTRACT: We developed a novel fabrication process for the stacked dense integration of a microring resonator (MRR) buried in a SiO2 cladding with vacuum cladding in the lateral direction. Owing to the vertical coupling and the lateral vacuum cladding, the radiation loss can be greatly reduced without affecting the coupling strength between the busline waveguide and the MRR. The reduction of radiation loss by ten orders of magnitude compared with the SiO2 buried cladding was theoretically and experimentally demonstrated. Using this technique, an ultracompact vertically coupled MRR with the ring radius of 5 mum was realized, and the free spectral range of 29 nm was successfully obtained.
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[show abstract]
[hide abstract]
ABSTRACT: To eliminate the scattering loss at the crossing points of cross-grid busline waveguides, the multilevel crossing structure of the busline waveguides was introduced into a vertically coupled microring resonator (VCMRR) filter. To achieve this structure, two fabrication technologies were newly developed; One is a method to planarize perfectly the top surface of each buried waveguide, and the other is a method to fabricate microring waveguides with very smooth sidewalls. Using the latter method, an ultracompact VCMRR with a ring radius of 5 mum was realized and a free spectral range of 37 nm was successfully demonstrated. Next, using the former method, single-ring and quadruple series-coupled ring resonators with multilevel crossing busline waveguides were fabricated. A clear filter response was obtained for the single-microring resonator, and a boxlike filter response was obtained for the quadruple series-coupled microring resonator with multilevel crossing busline waveguides.
